The present invention relates to a device for a prosthesis, and more specifically, a novel combination is shown, with a novel way of locking and opening an adjustment device for an artificial arm or leg.
On the market, there is available, a number of different solutions for artificial legs, for example. A such device is generally comprised of a tubular member which at its upper end is attached to a sleeve which is adapted to receive the stump of the leg, and it is further, by means of a second joint coupling fixed to a foot prosthesis or a corresponding device or member. It is important that the tubular member, when being attached to the stump, can be adjusted in both the angular and translatory direction, so that the user does not apply load in an unnatural way to the prosthesis and the stump, which would result in the pattern of motion of the prosthetic device becoming unnatural when the patient moves, and in that the knee joint and the muscles of the upper part of the leg may be loaded in an unnatural way.
The Swedish patent no. SE 454 046 shows such a device which, by means of an adjustment head 11 arranged at the upper end 4 of the tubular member 10, having a first member 16, allows setting of the angular position of the tubular member relative to an imagined load line. Moreover, other members 12, 13 allow a translatory displacement of the tubular member 10 relative to the adjustment head 11. The adjustment members 16 and 12, 13 respectively, allow a basic adjustment of the tubular member, once the prosthesis has been fitted.
Another Swedish patent, no. 360 257 of 1970, shows an adjustable coupling between two elements in an arm or leg prosthesis, or the like. Said device has a four-sided stud, having the shape of a truncated pyramid with four sides, divergently extending from the base. The device only allows angular adjustment in two defined planes in relation to the socket, but no translatory adjustment of the type disclosed in the Swedish patent SE 454 046 is provided for.
None of the prior art devices provide a prosthetic device which, without unnecessary disassembly or removal of the prosthesis, provides for a easy angular adjustment in all planes in relation to an imagined load line, and at the same time a translatory adjustment. Further, such systems do not normally combine easiness of disassembly, and an acceptable mechanical strength.
None of the known devices does, either, provide the possibility for a simple distal adjustment. The reasons necessitating such a length adjustment may be that the patient during the first trial is unwilling to fully load to the prosthesis, which makes it difficult to find the right length from the start. It is usually possible to see if the length of the prosthesis is wrong, only after the user of the prosthesis has gotten used to the prosthesis, and it would then be desirable to be able to make a fine adjustment of the length of the prosthesis. The adjustments in question are, then, often small adjustments in relation to the total length of the prosthesis, but these millimeters are important for the user of the prosthesis, in order to achieve a complete functional ability.
The present invention thus relates to a novel combination, with a novel way of locking and opening an adjustment device for a prosthesis. Said novel combination makes it easy to perform an adjustment of a prosthesis without the need to disassemble the prosthesis system, or the user having to remove the prosthesis. This facilitates the adjustment of a prosthesis in an important way, and it also provides another degree of freedom, by the addition of the possibility of distal adjustment.
In accordance with the present invention there is provided a locking ring for achieving a stable adjustable locking of the adjustment head against a coupling sleeve on the stump, also locking the translatory position of the prosthesis, which in an important way facilitates the translatory positioning of a leg prosthesis, since said prosthesis need not be disassembled or removed from the patient.
Thus, the present invention provides, by means of said locking ring, a stable and adjustable setting of the distal length of the prosthesis, which greatly facilitates adjustment of the length of the prosthesis, since it is no longer required that the prosthesis be disassembled or removed by the patient, in order to perform for such a fine adjustment of the length.
The object of the present invention is setting of the translatory position and distal length of the prosthesis by means of first adjustment means, and then an easy locking of the system in said position by means of the novel locking function. The upper part of the first adjustment means is resting against an upper coupling sleeve, which is fixed to the prosthesis sleeve. Said coupling sleeve has a central hole which allows the translatory displacement of a screw extending therethrough, in relation to the upper coupling sleeve. Said coupling sleeve also has a lower plane surface, against which the upper plane surface of the upper part of the adjustment head is abutting.
The upper part of the adjustment head comprises a first part of angular adjustment means, into a through hole into which the screw is screwed, and further it comprises the locking ring. The upper plane surface of the locking ring abuts against the plane surface of the coupling sleeve, and the position of the locking ring in relation to the upper part of the means for angular adjustment then determines the distal length of the prosthetic device. The adjustment head is further translatory adjustable in all directions in the plane of the coupling sleeve, and is locked in a stable way by means of the upper plane surface of the locking ring, the force of which is resisted by the central screw.
Additional adjustment means are used for the angular adjustment. Said additional adjustment means comprise an angular member, having a distal convex surface and a plurality of threaded holes inclining slightly upwards, into which adjustment screws, preferably of the socket head cap screw type, are used for providing the angular setting. At least three adjustment screws are required for achieving a stable angular setting, and for practical reasons, there should be no more than five screws. The adjustment screws are then screwed against a second part of the angular adjustment means for achieving an angular adjustment. The angular adjustment means (FIG. 2 and FIG. 3) may be comprised of, one the one hand, a pyramid adapter, which in turn is comprised of a pyramid adapter stud, and a convex outer surface arranged around said stud, which is attached, in a manner which is known to the artisan, e.g. to a an artificial foot, an artificial knee joint or a tubular prosthesis member. The pyramid adapter has a number of planes which correspond to the number of adjustment screws, said planes having an inclination such, that they lie mainly at right angles in relation to the adjustment screws. Further, the adjustment head is provided with a sleeve member having a concave surface, which rests against a convex surface around the pyramid adapter pin, thus taking up the axial load on the adjustment element, while the locking screws lock the angular position.
The angular means may on the other hand, in a second embodiment, be comprised of a tubular sleeve member which, in turn, has an inner, spherical surface which is attached to a support plate, the plane side of which essentially corresponds to the inclination of the end of a second screw member, which is screwed through the flange of the tubular sleeve member.